Heretofore, in systems providing services to users via a network, various techniques have been used to ensure confidentiality of data that is transmitted and/or received, and also security of user certification. For example, it is disclosed in JP2011-27917A that after carrying out certification using certification information such as user IDs, a client terminal transmits encrypted data to a server device, and the server device stores the encrypted data. Furthermore, in JP2010-79795A it is disclosed that by assigning a unique application ID to each of an application being delivered to a client terminal, application IDs can be used for certifying applications.